Train Stops
Train stops, also known as trips, tripcocks and tripstops, are devices fitted to most signals. They help to reduce the consequences of SPADs (signal passed at danger) by stopping the train at a red signal. How it works Train stops are connected to a signal. When that signal shows a red signal, the trip arm will come up. If a train tries to go past the signal, the arm will strike the trip cock on the train, which then will apply the emergency brakes on the train. Because the emergency brake has been applied, the train stops and can't move for a short time, because the brake pipe has to refill. This will increase the chance that the driver will noticed that a SPAD has occured, however they will not fully prevent collisions. This is because the driver can simply proceed after recharging the brakes, especially if they have been authorised by the signal box. This problem caused the Glenbrook train disaster where a V set tripping past a failed signal collided with the back of the Indian Pacific. In some cases, when the signal is displaying a shunt ahead aspect, the train stop will also not drop. This ensures that the train moves past the signal at a slow enough speed, ready to stop short of an obstruction. This is because the shunt ahead indication does not show that the line ahead is clear and is commonly used when signals, track circuits or other equipment have failed. Special Train Stops Low speed train stop This is a type of train stop attached to a signal that can display a low speed indication. The trip arm still works normally while the signal is at stop. However, when the signal is changed to low speed, the arm will stay up. As the train approaches the signal, sensors will measure the speed of the train, by counting how long it takes for the train to pass a certain section. If the speed is under 25km/h, the trip arm will drop and the train will be able to pass. However, if the train is over 25km/h, the train will strike the trip and be brought to a halt. Intermediate trips These trips are only found in major stations that have trains very close to each other. They are found along the length of a platform, seemingly not connected to any signal. However, they are connected to the signal at the end of the platform. When the signal at the end of the platform is at stop, all the trips will come up and act like a low speed trip. They will force the train to slow down for the red signal. The last trip, closest to the signal, requires a speed of about 4km/h. Fixed train stops These are train stops that are stuck in the up position, to protect dead ends. They normally have the shape of a triangular prism. Reverse Direction When the train is going backwards through the train stop for any reason (e.g. bidirectional signalling), the train stop will come down even if it is at stop. This is because the tripcock at the back of the train can be struck. Category:Miscellaneous Category:Railway equipment